Primary only control quasi resonant convertor

ABSTRACT

A power supply apparatus and method of regulating is provided. A converter circuit includes a primary switching element and an auxiliary switching element. The auxiliary switching element is for transferring a reflected voltage signal. A transformer includes a primary and a secondary, the primary is coupled with the converter circuit. The primary and secondary each include a single winding. An output rectifier circuit is coupled with the secondary of the transformer. A resonant circuit is included in the converter circuit and is coupled with the primary. The resonant circuit includes one or more resonance capacitors that are configured for providing a transformer resonance. The transformer resonance comprises the reflected voltage signal, the capacitance of the one or more resonance capacitors and a parasitic capacitance of the transformer. The reflected voltage signal is reflected from the secondary to the primary. A virtual output voltage feedback loop provides an output voltage reference signal to the converter circuit via the resonant circuit. The converter circuit is responsive to the output voltage reference signal in regulating an output voltage.

RELATED APPLICATIONS

This patent application claims priority under 35 U.S.C. 119(e) of theU.S. Provisional Pat. App. No. 60/921,220, filed Mar. 29, 2007, entitled“PRIMARY ONLY CONSTANT VOLTAGE/CONSTANT CURRENT (CVCC) CONTROL IN QUASIRESONANT CONVERTOR,” which is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to the field of power supplies. Moreparticularly, the present invention relates to a primary only controlledquasi resonant converter.

BACKGROUND

In many applications a voltage regulator is required to provide avoltage within a predetermined range. Some circuits are subject touncertain and undesirable functioning and even irreparable damage if aninput power supply fall outside a certain range.

A functional block diagram of a prior art power supply apparatus 10 isshown in FIG. 1. The apparatus 10 generally includes a power converter12 coupled with a transformer 14 that is coupled with an outputrectifier 16. The output rectifier 16 is coupled with an outputcapacitor 19 at an output Vout. A regulation circuit 15 comprising anopto-coupler 17 and a voltage reference and error amplifier 18 iscoupled between the voltage converter 12 and the output Vout. The powerconverter 12 is configured to receive an unregulated DC voltage signal.The unregulated DC voltage signal is coupled to the transformer 14. Thetransformer 14 includes a primary 14P and a secondary 14S. Theunregulated DC voltage signal drives the primary 14P to produce anintermediate voltage signal. The intermediate voltage signal comprises astepped-up or stepped-down voltage signal derived from the voltagesignal that drove the primary 14P. The intermediate voltage signal iscoupled to the output rectifier 16. The output rectifier 16 rectifiesthe intermediate voltage signal to produce a regulated DC output voltagesignal. A feedback signal provided by the opto-coupler 17 is coupled tothe power converter for regulating the output voltage Vout.

A schematic diagram of a prior art regulated power supply 100 is shownin FIG. 1A. The power supply 100 includes a converter circuit 102coupled with a transformer 140. The transformer 140 is coupled with anoutput circuit 106. The converter circuit 102 includes a capacitor 110coupled across an input Vin and coupled with a primary 140P1 and 140P2of the transformer 140. A primary switch 112A and an auxiliary switch112B are coupled with the primary 140P1 and 140P2 respectively. A pulsewidth modulator (PWM) module 130 is coupled with a gate of the primaryswitch 112A. The output circuit 106 includes an output rectifying diode146 and a load or an output capacitor 150 coupled across a secondary140S of the transformer 140. The power supply 100 can include a voltageregulating circuit including optical coupler circuit 108 and a voltagereference and error amplifier 109. The power supply 100 uses the PWMmodule 130 to alter a duty cycle of the primary switch 112A. The opticalcoupler circuit 108 in cooperation with the voltage reference and erroramplifier 109 provides feedback to the PWM module 130. The PWM module130 accordingly adjusts the duty cycle of the primary switch 112A tocompensate for any variances in an output voltage Vout. Very often thepoint of failure for the power supply 100 is the opto-coupler 108. Theopto-coupler 108 and the voltage reference and error amplifier 109increase production cost of the power supply 100.

Accordingly, it is desirable to create a regulated power supply togreatly reduce a point of failure and to reduce production cost.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, a powersupply apparatus is provided. The power supply apparatus includes aconverter circuit including a primary switching element and an auxiliaryswitching element. The auxiliary switching element is for transferring areflected voltage signal. A transformer includes a primary and asecondary, the primary is coupled with the converter circuit. Theprimary includes a single winding and the secondary includes a singlewinding. An output rectifier circuit is coupled with the secondary ofthe transformer. A resonant circuit is included in the convertercircuit, the resonant circuit is coupled with the primary. The resonantcircuit includes one or more resonance capacitors where the one or moreresonance capacitors are configured for providing a transformerresonance. The transformer resonance comprises the reflected voltagesignal, the capacitance of the one or more resonance capacitors and aparasitic capacitance of the transformer. The reflected voltage signalis received at the resonant circuit via the auxiliary switching element.The reflected voltage signal is reflected from the secondary to theprimary.

In an exemplary embodiment, the power supply apparatus includes avirtual output voltage feedback loop providing an output voltagereference signal to the converter circuit via a voltage feedbackcircuit. The output voltage reference signal is generated from thereflected voltage signal. The converter circuit is responsive to theoutput voltage reference signal in regulating an output voltage. Thevoltage feedback circuit includes a voltage divider coupled with thecontroller and coupled with the primary for sampling the reflectedvoltage. The primary switching element and the auxiliary switchingelement each comprise an n-type MOSFET transistor. The first and thesecond resonance capacitors are coupled in parallel with the primary. Acontroller includes a pulse width modulation (PWM) circuit coupled withthe primary switching element. The converter circuit comprises a flybackconverter. Alternatively, the converter circuit can comprise one of aforward converter, a push-pull converter, a half bridge converter and afull bridge converter.

In accordance with a second aspect of the present invention, a method ofregulating a power supply apparatus is provided. The method includesgenerating a reflected voltage signal in a transformer comprising aprimary and a secondary. The reflected voltage signal is reflected fromthe secondary to the primary where the primary is coupled with aconverter circuit. The primary includes a single winding and thesecondary includes a single winding. The reflected voltage signal istransferred from the primary to the converter circuit. The convertercircuit includes a primary switching element and an auxiliary switchingelement. The auxiliary switching element is for transferring thereflected voltage signal. A transformer resonance is generated with aresonant circuit included in the converter circuit. The resonant circuitis coupled with the primary. The resonant circuit includes one or moreresonance capacitors where the one or more resonance capacitors areconfigured for providing the transformer resonance. The transformerresonance comprises the reflected voltage signal, the capacitance of theone or more resonance capacitors and a parasitic capacitance of thetransformer.

Other features of the present invention will become apparent fromconsideration of the following description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth in the appendedclaims. However, for purposes of explanation, several embodiments of theinvention are set forth in the following figures.

FIG. 1 illustrates a prior art functional block diagram of a powersupply apparatus.

FIG. 1A illustrates a prior art schematic diagram of a power supplyapparatus.

FIG. 2 illustrates a functional block diagram of a power supplyapparatus in accordance with an embodiment of the invention.

FIG. 3 illustrates a schematic diagram of a power supply apparatus inaccordance with an embodiment of the invention.

FIG. 4 illustrates a schematic diagram of a power supply apparatus inaccordance with an alternative embodiment of the invention.

FIG. 5 illustrates a waveform diagram of a power supply apparatus inaccordance with an embodiment of the invention.

FIG. 6 illustrates a process flow diagram of a method of regulating apower supply apparatus in accordance with an embodiment of theinvention.

DETAILED DESCRIPTION

In the following description, numerous details and alternatives are setforth for the purpose of explanation. However, one of ordinary skill inthe art will realize that the invention can be practiced without the useof these specific details. In other instances, well-known structures anddevices are shown in block diagram form in order not to obscure thedescription of the invention with unnecessary detail.

Turning to FIG. 2, a functional block diagram is shown for a powersupply apparatus 20 according to the present invention. The apparatus 20generally includes a power converter 22 coupled with a transformer 24that is coupled with an output rectifier 26. The output rectifier 26 iscoupled with an output capacitor 32. The power converter 22 and thetransformer 24 include a resonant circuit 27 coupled there between. Avirtual feedback loop 23 is coupled between the power converter 22 andthe output capacitor 32.

The power converter 22 is configured to receive an unregulated DCvoltage signal. The unregulated DC voltage signal is coupled to thetransformer 24. The transformer 24 includes a primary 24P and asecondary 24S. The unregulated DC voltage signal drives the primary 24Pto produce an intermediate voltage signal. The intermediate voltagesignal comprises a stepped-up or stepped-down voltage signal derivedfrom the voltage signal that drove the primary 24P. The intermediatevoltage signal is coupled to the output rectifier 26. The outputrectifier 26 rectifies the intermediate voltage signal to produce a DCoutput voltage signal. A transformer resonance is generated in thetransformer 24 using a reflected voltage signal and a parasiticcapacitance, both qualities of the transformer 24, as an energy source.The reflected voltage signal 25 is reflected from the secondary 24S tothe primary 24P. The reflected voltage signal is transferred from theprimary 24P to the power converter 22 via the resonant circuit 27. Theresonant circuit 27 facilitates the transformer resonance by providingcapacitive circuits used to exchange energy between the primary 24P andthe resonant circuit 27. The reflected voltage signal 25 is used as anoutput voltage reference signal of the output voltage Vout to regulatethe power converter 22. The virtual feedback loop 23 is realized by theresonant circuit 27 in cooperation with the primary 24P and the powerconverter 22.

Turning to FIG. 3, a schematic diagram is shown for a power supplyapparatus 300 according to the present invention. The apparatus 300generally includes a converter circuit 302 coupled with a transformer340 that is coupled with an output circuit 306. The output circuit 306is coupled with an output node Vout. A virtual output voltage feedbackloop 323 is coupled between the converter circuit 302 and the outputnode Vout. The power supply apparatus 300 is configured to receive anunregulated DC voltage signal at an input node Vin and to provide aregulated output voltage Vout that is suitable for many low voltageappliances such as computer laptops, cell phones and other hand helddevices. In an exemplary embodiment the output voltage Vout can be setwithin the range 5-40 VDC. Alternatively, the power supply apparatus 300can provide the output voltage Vout that is less than 5 VDC.

The converter circuit 302 is configured to receive the unregulated DCvoltage signal. The converter circuit 302 includes a power converter 322and a resonant circuit 327. In an exemplary embodiment, the convertercircuit 302 comprises a flyback converter. Alternatively, the convertercircuit 302 can comprise one of a forward converter, a push-pullconverter, a half-bridge converter and a full-bridge converter. In yetother alternatives, the converter circuit 302 can comprise otherconfigurations of switch mode power supplies known to a person of skillin the art. The resonant circuit 327 is coupled between a primary 340Pof the transformer 340 and the power converter 322.

The power converter 322 includes a first terminal of a primary switchingelement or primary switch 312 coupled to the input node Vin. A secondterminal of the primary switch 312 is coupled with a controller 330 anda third terminal of the primary switch 312 is coupled to a firstterminal of a resistor 336 and coupled with the controller 330. A secondterminal of the resistor 336 is coupled to a first terminal of theprimary 340P. An input capacitor 310 is coupled across the input nodeVin. A first terminal of a pull-up resistor 334 is coupled to the inputnode Vin. A second terminal of the pull-up resistor 334 is coupled withthe controller 330. A capacitor 332 is coupled between the secondterminal of the pull-up resistor 334 and a first terminal of a voltagedivider 326, 328. A floating or virtual ground 335 is coupled betweenthe second terminal of the resistor 336 and the first terminal of thevoltage divider 326, 328. An output of the controller 330 is coupled tothe floating ground 335. A second terminal of the voltage divider 326,328 is coupled to the controller 330 and the third terminal of thevoltage divider 326, 328 is coupled to a ‘−Vin node’. A first terminalof a capacitor 324 is coupled to the floating ground 335 and the secondterminal of the capacitor 324 is coupled to a cathode of a diode 319. Acathode of a diode 321 is coupled to the second terminal of the resistor334 and the anode of the diode 321 is coupled to the cathode of thediode 319. The anode of the diode 319 is coupled to a first terminal ofa capacitor 320.

A voltage feedback circuit 313 is included in the power converter 322.The voltage feedback circuit comprises the voltage divider 326, 328 anda lead 313A coupled between an input of the controller 330 and thesecond terminal of the voltage divider 326, 328. The voltage feedbackcircuit 313 is coupled with the first terminal of the primary 340Pthrough the floating ground 335. The voltage feedback circuit 313samples a reflected voltage that is described further below. The voltagefeedback circuit 313 can be used to regulate the output voltage Vout.

The primary switch 312 comprises a suitable switching device. In anexemplary embodiment, the primary switch 312 comprises an n-typemetal-oxide-semiconductor field-effect transistor (MOSFET) device.Alternatively, any other semiconductor switching device known to aperson of skill in the art can be substituted for the primary switch312. The controller 330 includes a pulse width modulation (PWM) circuit.The controller 330 regulates the duty cycle of the primary switch 312with the PWM circuit. The controller 330 can include a currentcomparator circuit (not shown) to use with a current feedback circuit(not shown) in regulating the duty cycle of the primary switch 312.Likewise, the controller 330 can include a voltage comparator circuit(not shown) to use with the voltage feedback circuit 313 in regulatingthe duty cycle of the primary switch 312.

The resonant circuit 327 includes a first terminal of an auxiliaryswitching element or auxiliary switch 314 coupled to the second terminalof the resistor 336 and coupled to the first terminal of the primary340P. The second terminal of the auxiliary switch is coupled to acathode of a diode 315 and coupled to an anode of a diode 317. A cathodeof the diode 317 is coupled to the −Vin node. A third terminal of theauxiliary switch 314 is coupled to a first terminal of a first resonancecapacitor 308. A second terminal of the first resonance capacitor 308 iscoupled to the −Vin node and coupled to a second terminal of the primary340P. A cathode of a diode 318 is coupled to a second terminal of thecapacitor 320 and a anode of the diode 318 is coupled to a firstterminal of a second resonance capacitor 309 and coupled to an anode ofthe diode 315. A second terminal of the second resonance capacitor 309is coupled to the −Vin node. A cathode of a diode 316 is coupled to theanode of the diode 315 and an anode of the diode 316 is coupled to thefirst terminal of the first resonance capacitor 308. The first andsecond resonance capacitors 308, 309 are coupled in parallel with theprimary 340P. Alternatively, the resonance capacitors can comprise aseries resonant circuit coupled with the primary 340P.

A resonant tank of the resonant circuit 327 includes the first andsecond resonance capacitors 308, 309 coupled with the diodes 315, 316and 317 which are coupled with the auxiliary switch 314 which is coupledin series with the first resonance capacitor 308, both the firstresonance capacitor 308 and the auxiliary switch 314 are coupled inparallel across the primary 340P. The resonant tank functions as a DCgenerator when oscillating to produce a voltage potential. The producedvoltage potential can be used to power the controller 330. A charge pumpcomprising the capacitor 320, the diode 319 and the capacitor 324 isused to store and to couple the produced voltage potential to thecontroller 330 through the diode 321. The auxiliary switch 314 cycles onand off as the resonant tank oscillates to produce a turn-on voltage forthe auxiliary switch 314. The turn-on voltage is a voltage valuerequired to operate or “turn-on” the auxiliary switch 314. The turn-onvoltage is generated with the reflected voltage and an oscillationenergy of the resonant tank. The turn-on voltage value can depend on acapacitance chosen for the first and the second resonance capacitors308, 309. The produced voltage potential can also depend on thecapacitance chosen for the first and the second resonance capacitors308, 309.

The transformer 340 comprises the primary 340P and a secondary 340S. Inan exemplary embodiment, the primary 340P and the secondary 340S caneach comprise a single winding. The output circuit 306 includes arectifier diode 346 and an output capacitor 350. An anode of therectifier diode 346 is coupled to a first terminal of the secondary340S. A cathode of the rectifier diode 346 is coupled to a firstterminal of the output capacitor 350 and coupled to the output nodeVout. A second terminal of the output capacitor 350 is coupled to a‘−Vout’ node, and coupled to a second terminal of the secondary 340S.Alternatively, the output circuit 306 can include an output rectifiercircuit comprising a half-wave rectifier. In still another embodiment,the output circuit 306 can include an output rectifier circuitcomprising a full-wave rectifier. A transformer resonance is generatedin the transformer 340 using the reflected voltage and a parasiticcapacitance of the transformer 340 and a capacitance of the first andsecond resonance capacitors 308, 309.

The auxiliary switch 314 comprises a suitable switching device. In anexemplary embodiment, the auxiliary switch 314 comprises an n-typemetal-oxide-semiconductor field-effect transistor (MOSFET) device.Alternatively, any other semiconductor switching device known to aperson of skill in the art can be substituted for the auxiliary switch314.

The virtual output voltage feedback loop 323 provides a virtual outputvoltage reference signal to the power converter 322 via the resonantcircuit 327. The resonant circuit 327 in cooperation with the primary340P and the power converter 322 provides the virtual output voltagefeedback loop 323. The virtual output voltage reference signal isgenerated from the reflected voltage signal. The power converter 322 isresponsive to the virtual output voltage reference signal in regulatingthe output voltage Vout. The voltage feedback circuit 313 including thevoltage divider 326, 328 is coupled with the primary 340P for samplingthe reflected voltage signal and providing the sampled reflected voltagesignal to the controller 330. The resonant circuit 327 also allowscontrol of a reset timing of the transformer and a zero current for therectifier diode 346.

Turning to FIG. 4, a schematic diagram is shown for a power supplyapparatus 400 according to an alternative embodiment of the presentinvention. The apparatus 400 generally includes a converter circuit 402coupled with a transformer 440 that is coupled with an output circuit406. The output circuit 406 is coupled with an output node Vout. Avirtual output voltage feedback loop (not shown) similar to the previousembodiment can be coupled between the converter circuit 402 and theoutput node Vout. The power supply apparatus 400 is configured toreceive an unregulated DC voltage signal at an input node Vin and toprovide a regulated output voltage Vout that is suitable for many lowvoltage appliances such as computer laptops, cell phones and other handheld devices. In an exemplary embodiment the output voltage Vout can beset within the range 5-40 VDC. Alternatively, the power supply apparatus400 can provide the output voltage Vout that is less than 5 VDC.

The converter circuit 402 is configured to receive the unregulated DCvoltage signal. The converter circuit 402 includes a first terminal of aprimary switching element or primary switch 412 coupled with an inputnode Vin and coupled with a first terminal of a primary 440P of thetransformer 440. A second terminal of the primary switch is coupled to acontroller 430 and a third terminal of the primary switch 412 is coupledwith the controller 430 and coupled to a first terminal of a resonancecapacitor 408. A second terminal of the resonance capacitor 408 iscoupled to a second terminal of the primary 440P and coupled with afirst terminal of an auxiliary switching element or an auxiliary switch414. A second terminal of the auxiliary switch 414 is coupled with thecontroller 430 and a third terminal of the auxiliary switch 414 iscoupled to a ‘−Vin’ node. The controller is coupled to the Vin node andcoupled to the −Vin node. The converter circuit 402 also includes aninput capacitor 410 and a resonance capacitor 408.

The output circuit 406 includes a rectifier diode 446 and an outputcapacitor 450. An anode of the rectifier diode 446 is coupled to a firstterminal of the secondary 440S. A cathode of the rectifier diode 446 iscoupled to a first terminal of the output capacitor 450 and coupled toan output node Vout. A second terminal of the output capacitor 450 iscoupled to a ‘−Vout’ node and coupled to a second terminal of thesecondary 440S. The controller 430 is configured to drive the primaryswitch 412 and the auxiliary switch 414. The resonance capacitor 408 isconfigured to function similar to the previous embodiment as a resonanttank with an inductance of the transformer 440. The transformer 440comprises the primary 440P and the secondary 440S. In an exemplaryembodiment, the primary 340P and the secondary 340S can each comprise asingle winding.

Turning to FIG. 5, a waveform diagram 500 is shown for the power supplyapparatus 300 in accordance with an embodiment of the present invention.A waveform ‘A’ depicts a current of the primary switch 312 shown at apoint 510. A current of the auxiliary switch 314 is shown at the point520. The current of the primary switch 312 at the point 510 isincreasing as the current of the auxiliary switch 314 at the point 520is decreasing. The waveform ‘B’ depicts a transformer current 530 of thesecondary 340S. In one embodiment, the transformer current 530 in thesecondary 340S is greatest when the current 520 through the auxiliaryswitch 314 is the lowest.

Turning to FIG. 6, a process flow diagram is shown for a method ofregulating the power supply apparatus 300 in accordance with the presentinvention. The process begins at the step 610. An unregulated DC voltagesignal is received at the input node Vin. At the step 620, the reflectedvoltage signal is generated in the transformer 340 comprising theprimary 340P and the secondary 340S. The reflected voltage signal isreflected from the secondary 340S to the primary 340P. In an exemplaryembodiment, the primary 340S comprises a single winding and thesecondary 340S comprises a single winding. At the step 630, thereflected voltage signal is transferred from the primary 340P to theconverter circuit 302. The converter circuit 302 including the primaryswitch 312 and the auxiliary switch 314. The auxiliary switch 314 isused for transferring the reflected signal to the converter circuit 302.

At the step 640, a transformer resonance is generated using the resonantcircuit 327. The resonant circuit 327 is coupled between the powerconverter 322 and the primary 340P. The resonant circuit 327 includesthe first resonance capacitor 308 and the second resonance capacitor309. The resonant circuit 327 facilitates the transformer resonance byproviding the first and second resonance capacitors 308, 309 used toexchange energy between the primary 340P and the resonant circuit 327.The transformer resonance includes the reflected voltage signal, thecapacitance of the first and second resonance capacitors 308, 309 andthe parasitic capacitance of the transformer 340. The reflected voltagesignal is received at the resonant circuit.

At the step 650, a virtual output voltage reference signal is providedto the power converter 322 via the resonant circuit 327. The resonantcircuit 327 in cooperation with the primary 340P and the power converter322 provides the virtual output voltage feedback loop 323. The virtualoutput voltage reference signal is generated from the reflected voltagesignal. The power converter 322 is responsive to the virtual outputvoltage reference signal in regulating the output voltage Vout. Thevoltage feedback circuit 313 including the voltage divider 326, 328 iscoupled with the primary 340P for sampling the reflected voltage signaland providing the sampled reflected voltage signal to the controller330. The controller 330 regulates the output voltage Vout by modifyingthe duty cycle of the primary switch 312 by comparing the sampledreflected voltage signal across the voltage divider 326, 328 with anoutput voltage reference value to determine a target duty cycle based onan output voltage requirement of the attached device. The turns ratio ofthe transformer 340 can be used to determine the target duty cycle sincethe output voltage is proportional to the sampled reflected voltagesignal.

The resonant tank of the resonant circuit 327 functions as a DCgenerator when oscillating to produce a voltage potential that can beused to power the controller 330. In an exemplary embodiment, theproduced voltage potential can be supplied without using an additionaltransformer winding that would be in addition to the single primarywinding 340P and the single secondary winding 340S. The auxiliary switch314 cycles on and off as the resonant tank of the resonant circuit 327oscillates to produce a turn-on voltage for the auxiliary switch 314. Inan exemplary embodiment, the auxiliary switch 314 can be selfoscillating to turn-on and off from the turn-on voltage generated withthe reflected voltage and the oscillation energy of the resonant tank ofthe resonant circuit 327. In another embodiment, the auxiliary switch314 can be cycled on and off or driven by the controller 330. In yetanother embodiment, the auxiliary switch 314 can be driven by a switchdriving circuit (not shown) that is external to the converter circuit302. The method 600 ends at the step 660.

While the invention has been described with reference to numerousspecific details, one of ordinary skill in the art will recognize thatthe invention can be embodied in other specific forms without departingfrom the spirit of the invention. Thus, one of ordinary skill in the artwill understand that the invention is not to be limited by the foregoingillustrative details, but rather is to be defined by the appendedclaims.

1. A power supply apparatus comprising: a converter circuit comprising aprimary switching element and an auxiliary switching element, theauxiliary switching element for transferring a reflected voltage signal;a transformer comprising a primary and a secondary, the primary coupledwith the converter circuit, the primary comprising a single winding andthe secondary comprising a single winding; an output rectifier circuitcoupled with the secondary of the transformer; and a resonant circuitincluded in the converter circuit, the resonant circuit being coupledwith the primary, the resonant circuit comprising one or more resonancecapacitors, the one or more resonance capacitors configured forproviding a transformer resonance, the transformer resonance comprisingthe reflected voltage signal, the capacitance of the one or moreresonance capacitors and a parasitic capacitance of the transformer, thereflected voltage signal received at the resonant circuit via theauxiliary switching element coupled to the primary, the reflectedvoltage signal being reflected from the secondary to the primary.
 2. Theapparatus of claim 1, further comprising a virtual output voltagefeedback loop, the virtual output voltage feedback loop providing anoutput voltage reference signal to the converter circuit via the voltagefeedback circuit, the output voltage reference signal being generatedfrom the reflected voltage signal, the output voltage reference signalbeing proportional to the reflected voltage signal sampled by thevoltage feedback circuit, the converter circuit responsive to the outputvoltage reference signal in regulating the output voltage.
 3. Theapparatus of claim 1, further comprising a voltage feedback circuitincluding a voltage divider coupled with a controller and coupled withthe primary for sampling the reflected voltage.
 4. The apparatus ofclaim 1, wherein the primary switching element and the auxiliaryswitching element each comprise an n-type MOSFET transistor.
 5. Theapparatus of claim 1, wherein the first and the second resonancecapacitors are coupled in parallel with the primary.
 6. The apparatus ofclaim 1, wherein a controller includes a pulse width modulation (PWM)circuit coupled with the primary switching element.
 7. The apparatus ofclaim 6, wherein the PWM circuit regulates a duty cycle of the primaryswitching element.
 8. The apparatus of claim 1, wherein the convertercircuit comprises a flyback converter.
 9. The apparatus of claim 1,wherein the converter circuit comprises one of a forward converter,push-pull converter, half bridge converter and a full bridge converter.10. The apparatus of claim 1, wherein the output rectifier circuitcomprises one of a diode, a half-wave rectifier, and a full-waverectifier.
 11. The apparatus of claim 1, further comprising an outputcapacitor coupled with the output rectifier circuit.
 12. The apparatusof claim 1, wherein a resonant tank of the resonant circuit includes theone or more resonance capacitors, coupled with one or more diodes,coupled with the auxiliary switching element, coupled with an inductanceof the primary.
 13. The apparatus of claim 12, wherein the resonant tankproduces a voltage potential used to power a controller.
 14. Theapparatus of claim 1, wherein a charge pump comprising one morecapacitors and a diode is used to store and to couple a produced voltagepotential to a controller.
 15. A method of regulating a power supplyapparatus comprising: generating a reflected voltage signal in atransformer comprising a primary and a secondary, the reflected voltagesignal being reflected from the secondary to the primary, the primarybeing coupled with a converter circuit, the primary comprising a singlewinding and the secondary comprising a single winding; transferring thereflected voltage signal from the primary to the converter circuit, theconverter circuit comprising a primary switching element and anauxiliary switching element coupled to the primary, the auxiliaryswitching element for transferring the reflected voltage signal; andgenerating a transformer resonance with a resonant circuit included inthe converter circuit, the resonant circuit being coupled with theprimary, the resonant circuit comprising one or more resonancecapacitors, the one or more resonance capacitors configured forproviding the transformer resonance, the transformer resonancecomprising the reflected voltage signal, the capacitance of the one ormore resonance capacitors and a parasitic capacitance of thetransformer.
 16. The method of claim 15, further comprising an outputrectifier circuit coupled with the secondary of the transformer.
 17. Themethod of claim 15, further comprising a virtual output voltage feedbackloop, the virtual output voltage feedback loop providing an outputvoltage reference signal to the converter circuit via the voltagefeedback circuit, the output voltage reference signal being generatedfrom the reflected voltage signal, the output voltage reference signalbeing proportional to the reflected voltage signal sampled by thevoltage feedback circuit, the converter circuit responsive to the outputvoltage reference signal in regulating the output voltage.
 18. Themethod of claim 15, further comprising controlling a reset timing of theprimary using the resonant circuit.
 19. The method of claim 15, furthercomprising a voltage feedback circuit including a voltage dividercoupled with a controller and coupled with the primary for sampling thereflected voltage.
 20. The method of claim 15, wherein the primaryswitching element and the auxiliary switching element each comprise ann-type MOSFET transistor.
 21. The method of claim 15, wherein the firstand the second resonance capacitors are coupled in parallel with theprimary.
 22. The method of claim 15, wherein a controller includes apulse width modulation (PWM) circuit coupled with the primary switchingelement.
 23. The method of claim 22, wherein the PWM circuit regulates aduty cycle of the primary switching element.
 24. The method of claim 15,wherein the converter circuit comprises a flyback converter.
 25. Themethod of claim 15, wherein the converter circuit comprises one of aforward converter, push-pull converter, half bridge converter and a fullbridge converter.
 26. The method of claim 16, wherein the outputrectifier circuit comprises one of a diode, a half-wave rectifier, and afull-wave rectifier.
 27. The method of claim 16, further comprising anoutput capacitor coupled with the output rectifier circuit.
 28. Themethod of claim 15, wherein the resonant tank of the resonant circuitfurther includes the auxiliary switching element and one or more diodescoupled with the auxiliary switching element, the one or more diodesalso coupled with the one or more resonance capacitors.
 29. The methodof claim 15, wherein a charge pump comprising one more capacitors and adiode is used to store and to couple a produced voltage potential to acontroller.
 30. The method of claim 28, wherein the resonant tankproduces a voltage potential used to power a controller.
 31. The methodof claim 28, wherein a produced voltage potential is supplied withoutusing an additional transformer winding in addition to a single primarywinding and a single secondary winding.
 32. The method of claim 28,wherein the auxiliary switching element is self-oscillating, theself-oscillating being driven by the reflected voltage and anoscillating energy of the resonant tank.
 33. The method of claim 28,wherein the auxiliary switching element is driven by a controller. 34.The method of claim 28, wherein the auxiliary switching element isdriven by a switch driving circuit that is external to the convertercircuit.
 35. A power supply apparatus comprising: an input capacitorcoupled across an input node; a converter circuit comprising a primaryswitching element and an auxiliary switching element, the auxiliaryswitching element for transferring a reflected voltage signal, theconverter circuit coupled with the input capacitor; a transformercomprising a primary and a secondary, the primary coupled with theconverter circuit, the primary comprising a single winding and thesecondary comprising a single winding; an output rectifier circuitcoupled with the secondary of the transformer; and a resonant circuitincluded in the converter circuit, the resonant circuit being coupledwith the primary, the resonant circuit comprising one or more resonancecapacitors, the one or more resonance capacitors configured forproviding a transformer resonance, the transformer resonance comprisingthe reflected voltage signal and the capacitance of the one or moreresonance capacitors, the reflected voltage signal received at theresonant circuit via the auxiliary switching element coupled to theprimary, the reflected voltage signal being reflected from the secondaryto the primary.
 36. The apparatus of claim 35, further comprising avirtual output voltage feedback loop, the virtual output voltagefeedback loop providing an output voltage reference signal to theconverter circuit via the voltage feedback circuit, the output voltagereference signal being generated from the reflected voltage signal, theoutput voltage reference signal being proportional to the reflectedvoltage signal sampled by the voltage feedback circuit, the convertercircuit responsive to the output voltage reference signal in regulatingthe output voltage.
 37. The apparatus of claim 35, further comprising avoltage feedback circuit including a voltage divider coupled with acontroller and coupled with the primary for sampling the reflectedvoltage.